1. Field of the Invention
The present invention relates to the field of cameras. More particularly, the present invention relates to an impact triggering mechanism for a conventional camera mounted on a rear view mirror of a vehicle.
2. Description of The Prior Art
Generally, when taking a picture, personal attention is required to take a photographic picture of an object. When a vehicle collision occurs instantly, there is no way to manually take a picture at the instant an accident has occurred. An impact actuated inertial switch is required to trigger a camera.
In the prior art inertial switch category, various devices employ spring biased movable masses to open or close an electrical circuit or do mechanical work when the device is subjected to a sudden acceleration change. The typical impact sensor utilizes a movable mass that is biased to a normal position by compressed springs or magnetic attraction. The movable mass is often shaped in the form of a spherical or metal ball and is constrained to move through a closed chamber against the restraining force of the biasing means upon receiving an inertial force from the proper direction. The following prior art references are relevant to the field of the present invention.
1. U.S. Pat. No. 5,134,255 issued to Tetrault et. al. on Jul. 28, 1992 for "Miniature Acceleration Switch" (hereafter the "Tetrault Patent").
2. U.S. Pat. No. 5,011,182 issued to Husby et al. on Apr. 30, 1991 for "Velocity Change Sensor With Contact Retainer" (hereafter the "Husby Patent").
3. U.S. Pat. No. 3,836,738 issued to Baland on Sep. 17, 1974 for "Impact Switch With Inertia Operated Toggle Linkage Actuator Mechanism" (hereafter the "Baland Patent").
4. U.S. Pat. No. 3,407,667 issued to Doeringsfeld on Oct. 29, 1968 for "Omnidirectional Inertial Trigger Apparatus" (hereafter the "Doeringsfeld Patent").
5. U.S. Pat. No. 3,332,060 issued to Liljequist on Jul. 18, 1967 for "Vehicle Deceleration Signalling Apparatus" (hereafter the "Liljequist Patent").
6. U.S. Pat. No. 2,888,530 issued to Horton on May 26, 1959 for "Impact Responsive Camera For Autombiles" (hereafter the "Horton Patent").
7. U.S. Pat. No. 2,879,349 issued to Thompson on Mar. 24, 1959 for "Safety Switch" (hereafter the "Thompson Patent").
The Tetrault Patent discloses a miniature acceleration electrical switch. It relates to electrical acceleration switches which have a mass movable in a housing against a spring bias in response to an applied acceleration. The miniature acceleration switch is responsive to a relatively small axial acceleration in order to close normally open contacts in the switch, in the presence of large laterally directed accelerations on the switch. It includes a hollow cylindrical casing closed at one end. Its other end is closed by a header having an insulated axial lead wire extending inwardly from the casing, and an electrically conductive ring secured peripherally to the casing. The casing has an internally conical guide sleeve which includes a freely rollable massive ball. A piston in the guide sleeve carries a contact member spaced by an expanded coil spring from the lead wire. The piston moves axially against the spring bias such that the contact member contacts the lead wire to close the normally open circuit switch.
The Husby Patent discloses a velocity change sensor with contact retainer. It relates to an accelerometer for sensing velocity changes particularly suited for passenger restraint systems in a motor vehicle for deploying an air bag. It includes a housing with contact blades and a contacting element. The contacting element is arranged to move toward the contact blades when a deceleration exceeding a threshold level is sensed. The contact retainer is provided to set the blades in a preselected position so that the blades are contacted by the contacting element simultaneously thereby improving the response time of the accelerometer. The contact blades are connected serially in an electrical circuit comprising a battery and an actuating mechanism. The actuating mechanism controls and deploys one or more air bags.
The Baland Patent discloses an inertia switch assembly utilized with an electrical circuit. the inertia responsive switch includes an over center linkage system, switch terminals operatively arranged with the linkage system and effective to move between open and closed positions, and an inertia member operatively connected to the linkage system so as to effectuate an opening or closing of the switch terminals when the inertia responsive member moves relative to the linkage system upon impact or high deceleration of the switch. The switch is sensitive to uniaxial impacts. The switch closes to complete a circuit effective to actuate a transmitter that emits a signal. The switch has special utility in an automatic crash signal device for aircraft.
The Doeringsfeld Patent discloses an omnidirectional acceleration sensor that will provide a unidirectional mechanical output. It includes a frame, a pivot pin, an arm member, a coil spring and a spherical ball in a cup. When an upward inertial force is received, the spherical ball will tend to move with the force in a direction away from the frame. The spherical ball will force the arm member to pivot about a pin in a clockwise direction. Similarly, a lateral force causes the ball to move out of the cup so that the arm pivots. The inertial force results in a mechanical movement of both ends of the arm member that can be utilized to perform useful work. The device is specially designed for a munitions fuse.
The Liljequist Patent discloses an inertia actuated electrical switching device and system responsive to changes in deceleration of a vehicle for varying the amount of light emitted from its rear warning lights. The deceleration sensitive arrangement is used to vary the current flow in an electrical circuit, which is a type utilizing a relatively freely movable mass forming an electrical bridge between two terminals in the circuit. The electrical circuit includes an elongate track, a mass being bias movable relative thereto in response to changes in velocity, and electrical resistance arranged so as to vary the electrical resistance interposed in the circuit dependent upon the relative position between the track and the mass.
The Horton Patent discloses a switch of impact type in an electrical circuit. It includes a base of a dielectric material, a permanent magnet which is a horse-shoe design, a steel ball, and a dish with the steel ball located within the dish. The steel ball is kept between the poles of the permanent magnet by the magnetic lines of the force between the poles. The magnetic attraction of the steel ball to the poles is intense enough to hold the steel ball in place. Upon impact, the steel ball would be thrown from its position in the center of the dish against the ring encircling the dish, and therefore the steel ball would be in contact with both the dish and the ring. The steel ball contacting both the dish and the ring would close the circuit. The intended, but not claimed, application of this device is the operation of a camera mounted in a vehicle. The switch would energize an electrical circuit causing an electromagnet to depress the push-button of the camera which actuates the shutter in the camera. The switch is mounted remotely from the camera and the camera is mounted in back of the vehicle.
The Thompson Patent discloses an electrical safety switch. The safety switch serves to interrupt an electrical circuit in a vehicle, airplane or the like, in the event of an accident or impact. The safety switch includes a movable metal ball that is adapted to be moved from a predetermined position upon impact so that an electrical circuit will be interrupted.
Most of the prior art inertial switch patents are designed for use with an electrical circuit. It will be desirable to eliminate the electrical output and rely entirely upon mechanical functions for impact triggering of a vehicle camera.
None of the prior art mechanical inertial switches are suitable for impact triggering of a vehicle camera. Most of the mechanical inertial switches require a very large impact for triggering, such as that associated with munitions or an aircraft impacting the ground at high velocities. Another category of inertial switches, mostly electrical, are designed to activate automobile air bags upon severe impacts. These are particularly designed to operate above some high threshold and to avoid false alarms. A vehicle camera trigger should be sensitive to relatively small impacts and a few false alarms are of little consequence.
The major design problem for a mechanical inertial trigger for a vehicle camera is that the trigger must provide a relatively large actuation force, in excess of one pound to depress the camera shutter release button, but must be capable of activation by relatively small impact loads, from any horizontal direction, on the order of several ounces.
In addition, a vehicle camera mechanical impact trigger should be designed for convenient location and mounting in the vehicle to facilitate servicing and manual operation by the vehicle occupants, while not interfering with other vehicle operation and usage.